Generally, a hydraulic excavator and hydraulic crane are widely known as a construction machine. In the case of the hydraulic excavator, for example, the construction machine is largely constituted by an automotive lower structure or vehicle, an upper revolving structure rotatably mounted on the automotive lower structure, and a working mechanism provided on a front side section of the upper revolving structure, for example, for up and down motions.
The upper revolving structure is provided with a revolving frame as its base, and an engine is mounted on the revolving frame along with an operator's seat. A floor panel is laid on the front side of the operator's seat, and vehicle control pedals and levers are provided with a front side section of the floor panel.
Some hydraulic excavators are furnished with a cab in such a way as to enclose the operator's seat. The cab-furnished type hydraulic excavators are often provided with an air conditioner to improve the working environment within the cab by supplying conditioned air like cool air or warm air.
On the other hand, hydraulic excavators have a class of small-size power shovels which are generally referred to as “mini power shovels.” A cab to be furnished on a mini power shovel is formed in a smaller size in conformity with the small machine size, and in such a case, for example an operator's seat is located over an engine to effectively utilize limited spaces within the cab.
Further, in the case of a cab on a small-size excavator, its inner space is too limited to find a place for installation of an air-conditioning unit. In order to solve this problem, attempts have thus far been made to accommodate an indoor air-conditioning unit of an air conditioning system in the ceiling of a cab (e.g., as proposed in Japanese Patent Laid-Open No. H11-334351).
By an air conditioning system, intake air is conditioned and conditioned air is blown into a cab from an indoor air conditioning unit thereby to keep the temperature within the cab at an adjusted comfortable level for the operator.
In this connection, in the case of the small-size excavator by the above-mentioned prior art, a compartment is provided in the ceiling to accommodate an air-conditioning unit. This necessarily results in a unignorable increase in cab ceiling height and in an undesirable increase in total height of the excavator.
The increase in total height of an excavator invites various problems, For example, in some cases it becomes necessary to dismantle the cab from the lower structure to put the excavator in a transport container, and to ship the cab separately from other parts of the machine. Further, one may face difficulties in putting the excavator into a garage.
The air conditioning system is composed of an indoor or internal air-conditioning unit, and outdoor or external units such as compressor and condenser. The outdoor units like compressor and condenser are usually mounted on the side of the engine of the vehicle body, and a coolant is circulated between the indoor and outdoor units through pipes.
Therefore, it is often found difficult to charge a coolant during a shipment of an excavator because the internal air-conditioning unit in the ceiling of the cab is disconnected from the compressor of the external unit, and this makes the assembling work very inefficiently. In addition, the coolant of the air-conditioning system has to be extracted prior to disconnecting pipes, at the time of dismantling the cab for the purpose of maintenance and service or for other reasons. This makes the maintenance work very inefficient and troublesome.